1. Field of the Invention
The invention relates to surgical implant devices. More particularly, the invention relates to arthroscopically usable surgical implant devices suitable for fixation of ligament grafts within bone tunnels. Still more particularly, the invention relates to devices and methods for the arthroscopic reconstruction of ligaments using soft tissue ligament grafts.
2. Description of the Prior Art
The reconstruction of ligaments including anterior cruciate ligaments (ACL) and posterior cruciate ligaments (PCL) using autologous ligament grafts, allografts or artificial grafts is well known. The ACL and PCL procedures may be performed arthroscopically and generally involve preparing a bone tunnel through the tibia and adjacent femur, placing a ligament graft extending between the two bone tunnels and securing each end of the graft within its respective tunnel.
One common method of ACL reconstruction employs the use of bone-tendon-bone (BTB) ligament grafts (harvested from the patella and tibia) where the bone block at each end of the graft is fixed within its respective tunnel by an interference screw secured within each tunnel between the tunnel wall and the adjacent bone block. The interference screw is aligned parallel to the axis of the tunnel and holds the bone block in the tunnel by wedging it against the tunnel wall opposite the screw and by engaging the bone block and the adjacent tunnel wall with the screw threads. Another common method employs the use of soft tissue grafts (semitendinosus, hamstring, achilles, quadriceps, etc.) where the ends of the graft are secured by an interference screw similarly interposed between the wall of the bone tunnel and the adjacent soft tissue of the graft.
One difference between the BTB and soft tissue graft procedures is that in the latter the screw merely deforms the resilient soft tissue temporarily. Thus, while the use of interference screws for ACL fixation is widely preferred over other methods, recent clinical and laboratory experience has found that soft tissue grafts secured with only an interference screw may experience graft laxity over time. This may result in loss of the requisite tension in the graft and consequent re-operation. One possible reason for graft laxity may be the longitudinal movement of the graft within the tunnel and past the interference screw during cyclic fatigue before healing occurs. This type of graft slippage does not occur in BTB grafts because the bone block attached to the tendon is positively engaged by the screw threads and cannot move beyond the interference screw.
Despite the possibility of graft laxity, soft tissue grafts are still viewed as beneficial because they do not leave the patella in a weakened state like BTB grafts.
It is accordingly an object of this invention to produce a device and method for securing a soft tissue ligament graft within a bone tunnel so as to prevent graft slippage from the tunnel.
It is another object of this invention to produce a device and method for providing additional secondary fixation to a soft tissue ligament graft secured within a bone tunnel by a primary fixation device.
It is a further object of this invention to produce a device and method for assuring that a soft tissue ligament graft secured in a bone tunnel by an interference screw remains secured by preventing the soft tissue graft from moving past the interference screw.